A closed type injector has a nozzle orifice diameter of 0.9 mm and maximum cross sectional area of passage between needle cone and the seat is $1.75 mm^{2}$ . Coefficient of discharge for the orifice is 0.85 and for the passage is 0.8. The injection pressure is 175 bar and the average pressure of charge during injection is 25 bar, when the needle cone is fully lifted up. Calculate the volume rate of flow per second of fuel through the injector and the velocity of jet at that instant. Take density of fuel equal to $850 kg/m^{3}$ .

Given data:

Diameter of orifice= d= 0.0009 mm

Area of passage=A= , Let P= pressure just before the orifice outlet, in Pa

The injection pressure means the pressure at inlet of the fuel injector =175 bar

The pressure of charge during injection means the pressure of the fuel when it has come out of the nozzle tip =25 bar.

, in Pa

, in Pa

i. Calculation of volume flow rate of fuel through injector, Q

We know, velocity of fuel jet =

Where= pressure difference causing the fuel flow

Since Q= area x velocity

Adding equations (B) and (C) we get,

ii. Calculation of velocity of jet at that instant

Substituting this value of P in equation (D) we get